Honeywell 7800 Series fault 32: Airflow Switch
Fault 32 means the combustion airflow interlock was not in the state the module required. Unlike fault 23 it is not tied to PREPURGE, so note the sequence step shown with it: an airflow loss while firing points to a different cause than one before light-off.
Diagnose this with AI
Try Free Boiler Diagnostic Upload a keypad photo, the fault history or a parameter export from your Honeywell 7800 Series. InduQT compares the evidence and suggests the next useful checks.
When it happens
- Any state where air must be proven: PREPURGE, ignition trials or RUN
Where it sits in the burner
Supervised function: Combustion air proving.
| Component | Signals to look at | How it fails |
|---|---|---|
| Combustion air proving switch | Combustion air proving switch, Combustion air pressure | Pressure or position switch out of adjustment; Welded, jumpered or miswired contact; Restricted combustion air path |
| Combustion air fan (FD / ID) | Combustion fan running, Combustion fan speed, Combustion air pressure, Fan motor current, Fan vibration | Fan motor or drive fault; Restricted combustion air path; Bearing wear or misalignment |
| Air damper, actuator and linkage | Air damper position, Firing rate | Damper or valve linkage slip; Actuator or feedback fault; Air/fuel ratio drift |
Likely causes and checks
1Air pressure falls near the switch setpoint while firing
- Points to it
- Trips at low fire or during modulation; marginal differential at the switch.
- Check
- Measure the differential at the switch across the firing range; a setpoint close to the low-fire differential will chatter.
2Fan or air path problem
- Points to it
- Fan noise change, overload or VSD fault near the trip.
- Check
- Inspect the fan and intake as Table 3 directs; check VSD fault history.
3Wiring or dirty contacts on the interlock
- Points to it
- Intermittent with vibration; no change in air flow.
- Check
- With the sequence held in PREPURGE (Run/Test switch), confirm line voltage at the interlock input; clean or replace switch contacts.
Telling it apart
- Fault 23 is the PREPURGE-specific airflow fault; fault 13 is airflow proven in STANDBY.
- Fault 30 (Running ILK) covers the whole running interlock string, which includes the airflow switch on many burners.
Evidence to collect
- Code 32 and sequence step
- Air switch differential at low and high fire
- Fan VSD or starter fault history
Work on fuel trains, burners, pressure vessels and electrical equipment must be done by qualified personnel following the manufacturer’s documentation and local codes. Never bypass a safety device or interlock.